I've always understood OP to mean "original post" or "opening post" or "original poster."
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For the sake of clarity: No, in no way was I being passive aggressive. I really don't care at all what you think of MD's, or anybody else's, type. Therefore, I have little to no reason to invest any feeling or effort in trying to get you to see otherwise. That may sound somewhat offensive to you (after all, most people like it when others value their opinion) but hopefully it at least relieves you of any feeling of me attacking you for your opinion.
But while we're on the topic:
If anything, this seems passive aggressive to me. FWIW.